Question: The scale on a map is 6cm : 1km. If the distance between two cities is 10km, how far apart in cm are the two cities on the map?
The scale means that every 6cm on the map corresponds to an actual distance of 1km. An actual distance of 10km is the same as 10 $\cdot$ 1km. The distance between the two cities on the map is 10 $\cdot$ 6cm, or 60cm.